Silicon carbide (SiC) has very excellent physical properties such as high melting point, great hardness, high electron mobility, and high breakdown voltage. Accordingly, silicon carbide is always an important industrial material that is applicable to many technical fields, for example, machinery industry, aerospace industry, and it is also applicable to a great amount of electronic devices. Particularly, silicon carbide plays an important role in those electronic devices with high frequency and high power due to its high electron mobility, high breakdown voltage, and durable in high-temperature environment.
Silicon carbide consisted of silicon layers and carbon layers interlaced with each other features more than 200 polytypes. Silicon carbide can be classified into cubic phase, hexagonal phase, and rhombohedral phase. Cubic silicon carbide is referred to β-SiC while other phases are referred to α-SiC. Cubic silicon carbide (also called 3C—SiC) has attracted a lot of interest since it has the highest electron mobility and anisotropic electrical property. Compared to silicon-based element, the band gap of silicon carbide is much wider such that it can prohibit electrons from being exited to conduction band due to heat. Leakage of electricity is occurred at a temperature higher than 250° C. for silicon-based materials but silicon carbide element is operative at 650° C. In addition, the breakdown voltage of silicon carbide reaches 3V/μm such that silicon carbide is applicable to high-power element. Silicon carbide is called a third-generation semiconductor material with wide band gap after silicon and gallium arsenide.
There are many manufacture methods used to produce silicon carbide. Amongst, chemical vapor deposition (CVD) is a main approach to deposit a silicon carbide thin film on a substrate. For example, approaches to manufacture silicon carbide includes furnace, hot-filament, rf-plasma, and microwave plasma chemical vapor depositions. For electronic device applications, furnace CVD is usually adopted in order to deposit an uniform signal crystal epi-layer of a large area. This approach can be classified into homo-epitaxy formation on a silicon carbide substrate and hetero-epitaxy formation on a silicon substrate or other crystal substrates.
Although furnace CVD can yield high film quality, the temperature in such a manufacturing process is 1300 to 1500° C., which is higher than many types of metal substrates or even is close to the melting point of the silicon substrate. This approach causes many problems such as interdiffusion and substrate warping due to different thermal expansion, and therefore the application of this approach is dramatically restricted. In addition, the thin films fabricated by hot-filament or plasma CVD are usually polycrystalline or amorphous films. These films have high defect and high grain boundary density, and therefore they are not applicable to electronic device applications. They usually serve as interposers or super hard protection layers.
Therefore, how to solve above problems and manufacturing silicon carbide thin films with high quality at low process temperature are important issues in this industry.